Hydrocyclones designed in accordance with the present invention are believed to exhibit improvements when considered in relation to the prior art. Problems arising with hydrocyclones designed in accordance with the prior art include:
1. Usually they are relatively long and often require comparatively more space in an installation, particularly where a large number of hydrocyclones are used. This may be a significant disadvantage in installations where the cost of space is large, such as on an oil production platform.
2. The prior art refers to a relatively high pressure differential between the inlet means for admission of the fluid mixture to the hydrocyclone and the outlet means for discharge of fluid having a relatively high concentration of less dense component. This characteristic of the prior art can have at least two unfavourable consequences--first, a higher inlet pressure may be required to operate the hydrocyclone, and second, the turndown ratio may be less ("turndown ratio" is the ratio of maximum to minimum flow rate at the hydrocyclone inlet/s of the fluid mixture for the available maximum inlet pressure and minimum outlet pressures at which the hydrocyclone may be operated).
3. Prior art hydrocyclones are often ill-suited to the separation of highly viscous fluids. With such fluids, the dissipation of vorticity and loss of kinetic energy can lead to poor separation of components.
4. Prior art hydrocyclones are often comparatively inefficient when applied to the separation of finely dispersed components.
5. Towards the second end of such hydrocyclones the flow can become unstable, often resulting in flow disturbances that reduce the separating effect.
6. In particular, an operational difficulty has been encountered when operating hydrocyclones of a type described by reference to PCT/AU83/00028. It has been found that hydrocyclones with a fourth portion of reduced diameter do not perform as expected. It was in fact found that this decreasing diameter caused a proportionally greater decrease in flow of the less or least dense component/s as compared to flow of more or most dense component/s thereby reducing the turndown ratio of the hydrocyclone, this being an undesirable effect.
Compared to the prior art, it is believed that a hydrocyclone according to the present invention can exhibit one or more of the following advantages relative to the prior art: